LIGHT
Light: Definition
Light is a form of energy that enables us to see things. Light starts from a source and bounces off objects which are perceived by our eyes and our brain processes this signal, which eventually enables us to see. Maxwell predicted that magnetic and electric fields travel in the form of waves and these waves move at the speed of light. This led Maxwell to predict that light itself was carried by electromagnetic waves which means that light is a form of electromagnetic radiation.
Nature of Light
Light behaves as a:
- ray, e.g. reflection
- wave, e.g. interference and diffraction
- particle, e.g. photoelectric effect
Laws of Reflection
Light incident on surface separating two media
When light travels from one medium to another medium it either:
- gets absorbed (absorption)
- bounces back (reflection)
- passes through or bends (refraction)
When light is incident on a plane mirror, most of it gets reflected, and some of it gets absorbed in the medium.
Characteristics of light
- Speed of light is given as c=λμ, where λ is its wavelength and μ is its frequency.
- Speed of light is a constant which is 2.998×108m/s or approximately 3.0×108m/s.
Reflection of light by other media
A medium that is polished well without any irregularities on its surface will cause regular reflection of light. For example, a plane mirror. But even then some light gets absorbed by the surface.
Laws of Reflection
The incident ray, reflected ray and the normal all lie in the same plane. Angle of incidence = Angle of reflection
[∠i=∠r]
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